A patient data set and an operating site during surgery are typically referenced to each other by using either anatomical indicia or—before an image data set is created—implants (bone or skin markers) that are applied to the patient. The implants are indicated simultaneously with an input device at a workstation and with a localization system on the patient.
A more general task relates to referencing between a data set (which describes geometrically the spatial model of a body) and the real physical environment in which the actual body is placed. For referencing, a three-dimensional position reference body is used on or applied to the real body. The position reference body consists of one or more elementary bodies (markers) whose 3-dimensional position can be detected with sensors and which define a fixed geometric reference with respect to the center of gravity of the body or to other reference volumes of the body. For the purpose of registration, the position reference body and/or its elementary bodies are correlated in the data model and in the physical world.
Unlike the present method, the German patent DE 197 47 427 describes a method and a device wherein the characteristic surface of bone structures is used for providing a reference between a data set and the operating site. DE 197 47 427 describes an individual template which carries 3-D localization markers and is applied to and/or screwed on a bone segment.
The method has the disadvantage that an expensive CAD-CAM model has to be produced from a patient data set before an individual template can be manufactured. With many surgical procedures, large areas of bone have to be exposed for applying the individual surface template, which makes the procedure unnecessarily invasive.